On Monday (the 16th) I am going to be on live TV talking about the conjunction of Venus and Mars, which will happen on the 21st (Saturday). In the western sky, just after sunset, you will see Venus and Mars come very close together, and it is this chance alignment as seen from Earth that we call a conjunction. Venus, for anyone who has been looking at the evening sky of late, is very very bright at the moment just after sunset. Mars, on the other hand, is much fainter, but knowing it is close to Venus this next week to ten days will help you find it.
The diagram below, which is a screen capture using SkySafari on my iPad, shows the sky at 6pm (18:00) as seen from London on Monday the 16th. As you can see, Venus is very bright and Mars is much fainter, at about 11 o’ clock to Venus if you imagine the face of a clock.
Both planets are currently in Pisces, and Venus is approaching the brightest it can be. It has a magnitude of this week (for an explanation of the magnitude system, see my blog here). Mars, as is obvious from the diagrams and if you look yourself, is much fainter; currently , making it times fainter! A magnitude of makes Mars easily visible, but it doesn’t jump out at you like Venus does.
If I zoom in a bit for a couple of these evenings, this is how things will look
To the naked eye, Venus and Mars will not be separable, but through binoculars or a small telescope you will be able to see enough detail to be able to see the small angular distance between them.
One of the theories for what the star of Bethlehem was (if it existed at all, and assuming it was not supernatural), is that it was a triple conjunction of Mars, Jupiter and Saturn. Modern sky simulation software has allowed us to show that this happened in 7 B.C., but it shouldn’t come as any surprise to anyone who knows their history that Jesus could not have been born after 4 B.C. because that is the year King Herod died. A conjunction between Venus and Jupiter, the two brightest planets, can be very spectacular.